split-brain research

Question 1

hemispheric lateralisation

Answer 1

the idea that the two halves of the brain are functionally different and that certain processes are specific to one hemisphere (e.g. language is in the left)

Question 2

split-brain studies

Answer 2

• unique group of individuals who had undergone a commissurotomy (corpus callosum and other tissues that connect the two hemispheres were cut in order to prevent frequent epileptic seizures)
• main communication line between the two hemispheres had been severed
• allowed Sperry to see the extent to which the two hemispheres were specialised for certain functions

Question 3

Sperry’s procedure

Answer 3

• devised a procedure in which an image would be conveyed to the right visual field (processed by the left hemisphere) and vice versa and the pps had to draw or describe what they saw
• in the ‘normal’ brain, the corpus callosum would immediately share information to give a complete picture of the visual world

Question 4

key findings from describing what you see

Answer 4

• when a picture was shown to the right visual field, they could easily describe what they saw
• but when the same picture was shown to the left visual field, they often couldn’t describe what they saw or reported seeing nothing at all
• the individual’s inability to describe objects in the left visual field is because of the lack of language centres in the right hemisphere

Question 5

evaluation: strengths of the methodology

Answer 5

• participants asked to stare at the ‘fixation point’ and the image would flash up for 1/10 of a second
• this means that split-brain individuals would not have time to move their eye across the image
• allowed Sperry to vary aspects of the basic procedure and ensured that only one hemisphere was receiving information at a time
• therefore he developed a very useful and well-controlled procedure

Question 6

evaluation: issues with generalisation

Answer 6

• there were only 11 pps in the procedure, all of which had a history of epileptic seizures
• it has been argued that this may have caused unique changes in the brain that may have influenced the findings
• it is also the case that not everyone’s surgeries would have been the exact same

Question 7

evaluation: clearly demonstrates lateralisation of function

Answer 7

• draws the main conclusion that the left is more geared towards analytic and verbal tasks whilst the right is more for spatial tasks
• research suggests that the left hemisphere is the analyser while the right is the synthesiser which is a key contribution to our understanding of brain processes
• increased validity of the research